1. Field of the Invention
The invention relates to a cooking system such as an induced draft, open fryer system, in which a burner is fired into a heat exchanger tube, from which heat is transferred to a cooking medium, such as shortening or oil, contained in a fryer vessel. More particularly, the invention relates to a cooking system including a heat exchanger tube having a substantially oval cross-section, wherein combustion gases are drawn through the heat exchanger tube to make multiple passes through a fryer vessel.
2. Description of the Related Art
Deep fat fryers, or gas fryers, are commercially used by restaurants, institutional kitchens, and fast food establishments for cooking a variety of food products, such as french fries, fish, fried chicken, and the like. Food products are cooked by immersing it within a vessel or pot that is filled with a heated cooking medium. The cooking medium may be heated using a flow of heated gas that is forced or drawn through flow passages that are in thermal communication with wall portions of the cooking vessel or are disposed within the vessel itself in order to increase the heat transfer to the cooking oil. In either case, however, maintaining a uniform temperature throughout a cooking zone of the cooking medium remains a difficult task.
In known cooking systems, a gas burner may force air into a plurality of parallel passages within the cooking medium to heat the cooking medium to the desired temperature, with the air forced out through the rear of the cooking system. The walls of a combustion chamber absorb heat from the combustion gases by heat radiation and convection. Several disadvantages are encountered with this type of cooking system. Such systems have a low thermal efficiency because the combustion gases are forced through the cooking system and do not remain in thermal contact with the cooking medium for a sufficient amount of time. In addition, because the combustion gases exit the rear of the cooking system, the combustion gases pass quickly through the system, and complete heat transfer is not achieved.